There has been contamination of groundwater with chromium and/or other heavy metals in some localities and most economical treatment and recycle of groundwater after heavy metal removal is desirable. Most heavy metals will precipitate as gelatinous hydroxides at pH from 8.5 to 9.5 but chromium, when present at a valence of VI, must be reduced to a valence of III in order to be removed by precipitation as an hydroxide. Reducing agents such as sodium sulfite will reduce the chromium VI to chromium III. This reduction has generally been carried out at pH of less than 4 but will also occur at an alkaline pH in the presence of a ferrous salt. Apparently the simultaneous reduction and precipitation aids the reduction reaction. The ferrous salt is converted to a ferric salt by the reduction and ferric salts, when made alkaline will coprecipitate with other heavy metals. Large quantities of water are normally handled in groundwater treatment. Further, the groundwater may contain up to about eight parts per million (ppm) of oxygen and this 8 ppm oxygen will react with stoichiometric quantities of a ferrous salt. If the ferrous salt alone is used then a sufficient quantity to first react with oxygen is needed and additional ferrous salt for chromate reduction is necessary. This results, finally, in a larger volume of ferric hydroxide precipitate. We have found that if the oxygen is consumed by reaction with a water soluble sulfite such as sodium sulfite that approximately a stoichiometric quantity of a ferrous salt is needed to reduce the chromium VI to chromium III. The sodium sulfite reacts to form an innocuous sodium sulfate which is also soluble. With chemistry as outlined, we have the basis of a lower cost treatment system wherein sufficient quantity of an alkali salt is added to react with the oxygen in the water; the pH is adjusted to approximately 7.5 to 9.5 with an alkali such as sodium hydroxide and a ferrous salt is added to reduce chromium VI to chromium III. Further, we have found adding excess ferrous or ferric salt results in coprecipitation of the chromium III and other heavy metals such as cobalt, nickel, zinc, cadmium, manganese, copper, and lead, with the ferric salt as hydroxides. When chromium VI alone is the water contaminant complete removal may be obtained at a pH 7.5 with sulfite and iron treatment as outlined. When heavy metals other than chromium are present, treatment with sulfite for chromium VI reduction and use of excess iron is necessary with optimum hydroxide precipitation occurring at pH of about 9.5. The metal hydroxides may be removed from the water prior to recycle by setting plus filtration, by filtration alone, by use of a cyclone separator or a centrifugal separator, etc. Flocculating agents may be added to a precipitation vessel in order to aid in settling and/or filtration. In one preferred system, the equipment is mounted on a trailer transportable with a tractor and requiring only quick connect flexible couplings to stationary tanks and electrical power to be operable. In the system the solids are preferably settled in a stationary tank and separated using a cyclone separator for further solid thickening ahead of a precoated filter. Many such equipment arrangements may be visualized based on principles as outlined.